The first steps have been taken to develop a
tomato that is resistant to Pepino mosaic virus, a disease that is especially
damaging in greenhouse tomato production. Click the image for more
information about it.

Tracking and Taming a Tomato Virus

A tomato that can stand up to
attack by a damaging virus in greenhouse production systems is being developed
by an Agricultural Research Service (ARS)
scientist.

ARS plant pathologist
Kai-Shu
Ling is studying the origins and evolution of Pepino mosaic virus (PepMV),
which can damage tomato fruit, stunt growth and leave the plant vulnerable to
other infections.

It's important to find tomatoes that resist the virus in the greenhouse. In
2006, some 652,000 metric tons of greenhouse tomatoes were produced in North
America.

Two PepMV strains that infect tomato plants in the United States show a
distinct genetic divergence from strains that infect tomato plants in Europe.
Ling, who works at the ARS
U.S.
Vegetable Laboratory in Charleston, S.C., studied the genetic makeup of
some PepMV strains found in South America, where the virus was first found. He
wanted to see if he could tease out the relationships between the PepMV strains
found in Europe, South America and the United States.

When Ling examined the makeup of U.S. PepMV strains, he observed a strong
similarity to the South American strains. One U.S. strain exhibited almost 99
percent of the same DNA sequence as a South American strain. Another U.S.
strain shared almost 91 percent of its genetic traits with a different South
American strain. However, European strains only shared from 78 percent to 86
percent of the genetic characteristics found in South American strains.

Ling also identified three varieties of wild tomatoes with a range of
genetic resistance to PepMV. He used the most robust of these varieties to
generate new progeny that remained symptom-free after they were exposed to
PepMV strains found in South America.

Ling will now use this symptom-free variety to see if he can create a tomato
plant with genetic resistance to two U.S. PepMV strains. If he succeeds, he
will try to develop a tomato type that has a more general resistance to the
European strain of PepMV.

Read
more about this research in the September 2008 issue of Agricultural
Research magazine.